MODS!!! Please do not toss this in the "what oil I should use" sticky. This topic has been lost in that thread many times already and its obviously still a problem. They see the 100 pages of posts and pass. This is also not about which oil they should use, it is about the importance of choosing the proper weight.
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Moderator's note: If this turns into a what brand to use i'll lock it.(i give it a day or two)
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I have seen and replied to countless posts noticing a fairly common thing. People are just completely clueless that oil weight has a huge effect on your oil pressure and temperature. Probably more of an adverse effect that having an undersized or over sized oil pump does.
Now as I've stated in a previous post, I cannot take credit for this. I read a post from [email protected] which kicked me into gear experimenting.
I've found that depending on what you've got... case type, bearing condition, oil galley size, single relief/dual relief, doghouse/non-doghouse coolers, external coolers and oil pump size all may require different oil weights for optimal cooling efficiency.
From the amount of testing I've done I have come to these conclusions; 1) 10w30 is the most commonly used oil weight and in about half of the engines I've checked, 10w30 is the best weight for them. These cases tend to be late model dual relief cases with 15mm oil galleys and a 26mm oil pump.

2) Single relief cases, especially those with small oil galleys LOVE light oil. 0w30 or 0w20. I use 0w30 because Brad Penn makes this weight.

3) I have not found one engine that needs 20w50. People seem to come to the conclusion that heavier oil cools better which, well it might be true. I don't know, but that thick of oil causes excessive oil pressure in ACVW engines which makes the oil bypass the oil cooler. No oil cooler = hot oil. Though it may or may not cool better, it does not work well in air cooled vw engines. The only time that thick of oil should be used is if you have excessively low oil pressure as if your mains were on their last leg or your oil pump needs replaced. Using 20w50 is a band-aid, not a fix.

You need to keep in mind, this is something that needs to be experimented with. I've had engines that the overheating issue was obviously caused by the oil pressure. Even with testing different weights I didn't get them down to where they should be so testing the weights might also include changing your 21mm oil pump to a 26mm or vice versa. I know it sounds like a lot of work but on engines with NO overheating issues I have commonly dropped the oil temps 15 degrees at 65mph... this is huge. My coolest running case is... are you ready for this? A single relief H case with 10mm oil galleys, 26mm oil pump using 0w30. It used to run 230 degrees at 70/75mph and I couldn't run it for more than 10 or 15 minutes at that speed which is about normal for an ACVW but once I switched a few things around, now its running 215/220 degrees at 75/80mph and I can run it for hours at this temp. Pretty cool huh? Pun intended.

This testing is pretty straight forward. Use 10w30 as a base line and having an oil pressure gauge makes it much easier but if not you will just be dropping oil a bit more. Make sure your oil pressure stays within range. The 10lbs per 1000RPM rule is good to stick by, Performance engines can have a bit more pressure.
Before even thinking about this testing you need to be sure you have ALL OF YOUR COOLING TINS! Yes... sled tins as well. Stock VW cooling systems are cheap and cool the best without spending too much. If you have a cheapo aftermarket shroud(commonly 36hp style), ditch it. They cool terribly 90% of the time and chances are they are causing most of your issues.

damn i didnt know this. our local parts shop has sold me lots of 20-50 oil and i always seem to have an oil leak some were. rear main blown, fixed it. valve covers leaking, fixed it. now i have a leak coming somewere from the upper head studs under the tins im changing it tomorrow!!!

Thank you; useful info neatly condensed. The 'what oil' thread has become so bulky and protracted as to be effectively useless to anyone looking for information on this topic._________________Do not follow me, for I may not lead. Do not lead me, for I may not follow. Do not walk beside me either; actually just bugger off and stand over there will you.

damn i didnt know this. our local parts shop has sold me lots of 20-50 oil and i always seem to have an oil leak some were. rear main blown, fixed it. valve covers leaking, fixed it. now i have a leak coming somewere from the upper head studs under the tins im changing it tomorrow!!!

20w50 = too much pressure = leaks everywhere. Being as the leaks are already there chances are switching will not do much, you will need to pull it out and have your way with it. Make sure its not your oil cooler leaking, if it is pull it out and do a pressure test on it. 70lbs of air through it is enough then toss it under water. You can make something using an old oil cooler stand and an air hose connector.

damn i didnt know this. our local parts shop has sold me lots of 20-50 oil and i always seem to have an oil leak some were. rear main blown, fixed it. valve covers leaking, fixed it. now i have a leak coming somewere from the upper head studs under the tins im changing it tomorrow!!!

Those are two different oils, 0W-30 is great for colder temps and works well in air cooled engines at startup where FLOW is critical. At operating temps both oils are the same from a viscosity standpoint.

I got a tip on a big sale of a synthetic 20-50 and bought boxes of the stuff.
Have been using it for years and no leaks. As most people believe synthetics are more prone to leaks, not in this case. The engine has 100k on it and the only leak is the drain plug washer, which I reused.

It is a T-4 and they do have better push rod tubes.

Hey like some of the guys said they run stright 30 no problems.

Leaks on aircooled engines are a part of life, that burnt oil smell is a normal part of the aircooled thing. That said, after 50 years that air cooled performance has been around most engine builders have got real good at thinking ahead to prevent oil leaks. So we see alot less._________________site: www.nextgen-usa.com
email: [email protected]
or
[email protected]
The Type IV Upright Conversion Manual

New engine under 3500k
New England, cold winters and summer temps in the 90s
Beetle sedan, late model solid decklid top propped
Stock Type 1 oil cooler, no secondary cooler, full flowed
Flaps and thermostat installed along with all factory tin
Bug Pack 36'er shroud with proper mods to mimic German shroud

I use green 10W30. My engine is big and runs cool at 180* around town [through the filter mount] and 190-210* on the highway at speed or faster. I still need to fatt'n up the jetting, so I will update if temps are affected. Oil temps are monitered through an Auto Meter Sport Comp electrical gauge. I backup the temp readings with a calibrated Mainely oil temp dipstick and the occasional GBE temp stick. [/b]

edited: I will add that my oil pressure readings are also from an Auto Meter Sport Comp electrical gauge and to verify, a mechanical gauge t'd at factory pressure sender location. I get 60lbs. cold start with current temps outside and 10lbs. per 1000rpms all the way up to 210* operating temp. The idle pressure drops to zero on both gauges after 190-200* operating temp, but they can be off since they are just cheap gauges. I never see the factory light flicker and the key off test proves good pressure. A touch of the throttle shoots pressure up to 45-60lbs. no matter what temp the engine oil is at. I have also varified good pressure per the "Official VW Manual", not a knock off.

Last edited by wildman1 on Thu Jun 09, 2011 8:50 am; edited 1 time in total

I run and recommend straight 30 for solid lifter engines and 20W50 for hydraulic lifter engines.

What if the engine was sold to someone in Alaska?

Ya know what. I did forget about the hydro's. I do not have enough knowledge on them to really say much about it but I have read that VW recommended thicker oil in these engines from the factory, also a larger 30mm oil pump I believe.
Roy, do you have numbers as to what these types of engines run oil pressure and temp wise?